1. Field of the Invention
This invention relates to new auxiliaries for use in the production and processing of crude oil.
2. Statement of the Prior Art
In view of the high price of crude oil, petroleum containing a relatively high proportion of paraffin hydrocarbons, which hydrocarbons are solid at room temperature, is being produced and processed to an increasing extent. Oils such as these lose their fluidity on cooling from the generally high temperature of the oil reservoir to ambient temperature through the crystallization of relatively high melting constituents. In order, therefore, to avoid difficulties during production, transport and processing, it is standard practice to add pour point depressants, also known as flow promoters or crystallization inhibitors.
Several such pour point depressants are already known. Thus, U.S. Pat. Nos. 3,904,385 and 3,951,929, as well as corresponding German Application No. 22 64 328 describe the use of polymeric acrylates containing from 18 to 24 carbon atoms in the alcohol moiety. The disadvantage of these polymeric acrylates is that they have to be used in relatively high concentrations of from 0.01 to 3% by weight, based on the weight of the petroleum.
Copolymers of long-chain acrylic or methacrylic acid esters and 4-vinyl pyridine are described for the same utility in U.S. Pat. No. 3,957,659, as well as corresponding German Application No. 22 10 431 and in U.S. Pat. No. 4,110,283, as well as corresponding German Application No. 26 12 757. The copolymers in question are used in concentrations of from 200 to 2000 ppm. The disadvantage of these copolymers is that they are comparatively expensive because 4-vinyl pyridine is difficult to obtain on a commercial scale.
British Patent Specification No. 2,058,825, as well as corresponding German Application No. 29 26 474 describe copolymers of long-chain acrylic acid esters, namely esters of "Ziegler-process" alcohols, and dimethylaminoalkyl acrylic acid esters or methacrylic acid esters for use as pour point depressants. Particular emphasis is placed on the shear stability of the products and also their effectiveness in concentrations of from 50 to 350 ppm. However, it is known that esters of the type in question (containing dialkylamino groups) can undergo hydrolysis in the presence of water, resulting in the formation of amphoteric, largely insoluble and hence ineffectual polymers. Finally, British Patent Specification No. 2,082,604, as well as corresponding German Application No. 30 31 900 describe a copolymer of long-chain acrylates and maleic acid anhydride as a pour point depressant. The disadvantage of using this copolymer is that, because of their high reactivity, the anhydride groups are capable of further reacting to form acids which might possibly promote corrosion.